A TDD denotes technology for time-dividing a signal frame of the same frequency band according to an uplink and a downlink, and supporting bidirectional transmission.
As compared to Frequency Division Duplexing (hereinafter, referred to as FDD) in which different frequency bands are used for uplink and downlink signals, a TDD is suitable for the transmission of an asymmetric or burst application by dynamically allocating time slots, can support the same transmission speed by using few time slots, and can provide a service by using ½ frequency as compared to the FDD.
Such a TDD has been recognized as attractive technology to a communication provider intended for proving of a portable Internet service at low cost, and has attracted public attention as important technology for proving a portable Internet service. However, a TDD is disadvantageous in that the timing and synchronization processes of an application according to the dynamic allocation of a time slot are very difficult.
Accordingly, in a wireless communication system using a TDD, a synchronization process is necessary. For the synchronization process, a preamble must be detected. In order to detect the preamble, it is necessary to detect the boundary of a downlink frame including the preamble.